Reliability and validity of the Thai version of the Rapid Mood Screener (RMS-T)

Purpose: Bipolar disorder (BD) is frequently misdiagnosed as unipolar depression, leading to inappropriate treatment and adverse outcomes. The Rapid Mood Screener (RMS) was developed to improve BD detection, a prerequisite for improving health outcomes in BD. This study aimed to translate and culturally adapt the RMS into Thai (RMS-T) and to evaluate its psychometric properties in Thai adults with bipolar I disorder (BD-I) and bipolar II disorder (BD-II). Methods: The RMS was translated using forward–backward translation and cultural adaptation. Participants included outpatients at a tertiary psychiatric clinic with diagnosed major depressive disorder (MDD; n = 109) and BD (n = 31; BD-I = 21, BD-II = 10). Psychometric properties included internal consistency, item-total correlations, test–retest reliability, and criterion validity against the Mini International Neuropsychiatric Interview (MINI-5). Receiver operating characteristic (ROC) analyses compared RMS-T with the Thai Mood Disorder Questionnaire (T-MDQ), and optimal cutoffs were determined using Youden’s index. Results: Internal consistency was acceptable for a brief six-item screening tool (Cronbach’s alpha = 0.610; McDonald’s Omega = 0.632). RMS-T demonstrated good discriminative ability for BD (AUC = 0.805), comparable to T-MDQ. Optimal cutoffs were ≥ 4 for BD (sensitivity 64.5%, specificity 78.9%, Youden’s index 0.43). Test–retest reliability was strong. Conclusion: The RMS-T is a valid, practical, and time-efficient screening tool for BD patients presenting with depressive episodes. Further research should investigate end-user satisfaction, the impact on health outcomes, clinical utility, and cost-effectiveness in broader settings and populations.